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Population

GeneticsStudy of Microevolution

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Gene Pools

A population’s gene gene poolpool is the total of all genes in the population at any one time. 

•PopulationPopulation - a localized group of individuals of the same species. 

•SpeciesSpecies - a group of populations whose individuals have the ability to breed and produce fertile offspring. 

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The Gene PoolThe Gene Pool

•Different species do NOT exchange genes by interbreeding

•Different species that interbreed often produce sterile or less viable offspring e.g. Mule

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The Hardy-Weinberg TheoremThe Hardy-Weinberg Theorem

•Idealized mathematical model of gene pools.

•Predicts a relationship between -allele frequencies in the gamete pool -genotype frequencies in the next

generation

•Used to describe a non-evolving population.non-evolving population. 

• Natural populations are NOT expected to actually be in Hardy-Weinberg equilibrium.

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Assumptions of the H-W TheoremAssumptions of the H-W Theorem

1. Organism is diploid2. Generations are nonoverlapping3. Large population size4. No net mutations5. Reproduction is sexual6. Random mating7. No migration 8. No natural selection

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Causes of microevolution :(changes in gene pools)

                       

1. Natural selection

2. Genetic drift

3. Mutation

4. Gene Flow

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English Peppered Moth

Sickle Cell and Malaria

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Gene Flow genetic

exchange due to the

migration of fertile

individuals or gametes between

populations.

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The original source of variation.

Beneficial mutations are favored by natural selection and so increase in frequency in the gene pool  Mutations can be transmitted in gametes to offspring, and immediately affect the composition of the gene pool.

Mutations

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Why is genetic variation important?

variation

no variation

EXTINCTION!!

globalwarming survival

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Genetic drift

the alteration of the gene pool of a small population due to chance

may cause genetic drift:                   

Founder effect

Bottleneck effect